Minimally invasive ultrasound-guided biopsy of the common extensor tendon enthesis: a cadaveric study to standardise the technique

Abstract

Objective: To develop and validate a minimally invasive ultrasound (US)-guided biopsy technique to collect entheseal tissue from the common extensor tendon (CET) enthesis at the lateral humeral epicondyle.

Methods: Seven sonographers performed a US examination of the CET on six human cadaveric upper limbs to locate the enthesis using an anatomical landmark-based approach. An adapted mini-arthroscopic system was introduced under US guidance to the target site for sample collection. At the end of the procedure, a dye was injected through the guide needle, followed by dissection, to confirm the sampling location. Histology and immunohistochemistry analyses were performed to assess the quality and representativeness of the samples. The reliability of the procedure among operators was evaluated by analysing the rate of successful sampling.

Results: 24 samples were collected. The target site to be biopsied was identified as the insertion of the extensor carpi radialis brevis component of the CET. On dissection, the stain used to verify sampling accuracy was confirmed within the defined target area, with no damage to adjacent structures. Histology and immunohistochemistry indicated that most of the samples exhibited characteristics consistent with entheseal tissue (21 out of 24). All participants identified the CET and successfully completed the procedure, demonstrating reliable sample quality across operators.

Conclusion: We developed a landmark-based approach to perform a minimally invasive full controlled US-guided biopsy of the CET enthesis that showed to be feasible and reproducible. We believe that this standardised, minimally invasive technique will widespread a reliable collection of entheseal tissue for future clinical and translational studies.

Keywords: Arthritis, Psoriatic; Tendinopathy; Ultrasonography.

Figure 1. Longitudinal view of the CET enthesis to perform the ultrasound-guided biopsy. (A) Longitudinal view of the CET complex, evidencing the proposed landmark-based approach to identify the RCL. (B) Longitudinal view of the CET complex in the final position for CET enthesis biopsy. CET, common extensor tendon; ECRB, extensor carpi radialis brevis; EDC, extensor digitorum communis; RCL, radial collateral ligament. ˆAnterior tubercle; *fibrocartilage.

Figure 2. Minimally invasive US-guided biopsy technique of the CET enthesis. (A) US-guided biopsy technique, the guide needle (arrow) is inserted up to the target area of the CET enthesis (dashed line) where the tip of the nano-forceps is opened to collect tissue (arrowhead). (B) Nano-forceps tips with the entheseal sample collected. CET, common extensor tendon; US, ultrasound.

Figure 3. Post-procedural dissection of the lateral epicondyle. (A) Representative picture of the correct location of the green dye injected at the end of the procedure at the level of the CET insertion. (B) Representative picture showing the absence of muscle or tendon injuries in the trajectory of the biopsy instruments. CET, common extensor tendon; 1, extensor carpi radialis longus; 2, extensor carpi radialis brevis; 3, extensor digitorum communis; 4, extensor digiti minimi; 5, extensor carpi ulnaris; 6, supinator.

Figure 4. Histology of entheseal samples from the CET. (A–C) Representative pictures of entheseal tissue by H&E (A), MT (B) and Safranin O (C), respectively, with inset showing the area of fibrocartilage. Original magnification ×100, ×400 (insets). Scale bars, 200 μm and 50 μm. (D–F) Representative pictures of immunostaining for aggrecan (D), collagen type II (E) and collagen type X (F) with insets. Original magnification ×200, ×630 (insets). Scale bars, 100 μm and 30 μm. CET, common extensor tendon; H&E: haematoxylin and eosin; MT, Masson’s trichrome.